As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option is an Information Handling System (IHS). An IHS generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes. Because technology and information handling needs and requirements may vary between different applications, IHSs may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in IHSs allow for IHSs to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, global communications, etc. In addition, IHSs may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
There is a trend to deploy low-voltage Battery Backup Units (BBUs) inside an IHS as a distributed Uninterruptible Power Supply (UPS), therefore replacing traditional central AC UPS systems. In the event of an AC power interruption, the battery backup unit (BBU) may take over the load of the IHS (i.e., equipment that is powered by the BBUs and power supply units or “PSUs”) in real time and maintain continuous powering of the IHS for a period of time sufficient to switch over to an alternative power source or to complete an orderly shutdown.
Once the AC power source or the alternative power source (usually a backup generator) is up and ready, the load is transferred from all the BBUs back to the PSUs powered by the AC power sources. If such a power transfer happens simultaneously across all IHSs in the data center, however, the abrupt heavy loading (typically in the order of less than one second) can be much faster than the inertia/response speed of a backup generator, and may overload the backup generator, leading to its shutdown.
A conventional approach to avoiding such an overloading and shutdown includes adopting a randomized transition at data center level—i.e., each IHS's power transfer is initiated at a randomized time within, for instance, a 10-second window. In this way, the aggregated loading at the data center level is increased gradually and progressively. Depending on the outage time, this transition time period may be programmed differently. However, even with such schemes, load transition on each individual IHS still happens abruptly.
Controlled load transition techniques—that is, reloading the AC line/backup generator incrementally after operating on battery power—are referred to as “walk-in,” which is defined in various specifications. For example, some specifications may define that a walk-in ramp shall not present input power steps greater than 200 W per second on the PSU AC cord input to a 1,600 W PSU, which means that the whole period of walk-in for all the PSUs is around 10 seconds. In some cases, conventional walk-in transitions may be implemented within a battery backup function inside every PSU, and the battery is interfaced with the PSU circuits at the primary 400 V bus point. In those cases, the linear load ramp or walk-in process mostly relies upon the internal control within each PSU.
The inventors hereof have recognized, however, that in more general applications (e.g., large data centers), PSUs and BBUs may be housed in separated units and placed in parallel operation with shared output DC bus (such as 12 V bus, or the like). To address these, and other concerns, the inventors hereof have developed systems and methods for controlling load transition between PSUs and BBUs as described herein.